Process for making carboxylic acids from nitrohydrocarbons



rarefied Apr. a, teas units sates arrests attain amuse rare to Commercial doiventa il'lorporation. 'llerre iliaute, End, a corporation oi? Maryland No Drawing. Application June lid, 1937, heriiai No. lidhditt 7 came. (or. zoo-n12) My invention relates to the production of carboxylic acids. More specifically, my invention re lates to the production of carboxylic acids from iii) . materials in any suitable manner.

primary nitrohydrocarbons.

The primary nitrohydrocarbons may be ob tained according to a number of different reactions, but are most economically produced by vapor phase nitration of saturated hydrocarbons in accordance with the process or" U. S. Patent 1,967,667 by H. B. Hass, E. B. Hodge and B. M. Vanderbilt. The nitroparaflins produced by this process from petroleum hydrocarbons constitute an advantageously cheap source of aliphatic' compounds for the production of organic chemicals. I I have now found that carboxylic acids may be produced from these nitrohydrccarbons with consistently satisfactory yields and conversions, by reacting the nitrohydrocarbons with certain halogenated acids under the controlled conditions hereinafter set forth.

The process of my present inventionmay be briefly described as comprising subjecting the primary nitrohydrocarbon, preferably at a temperature of 100C. to 160 C., to the action of at least one mol. of an. alpha-halogenated fatty acid containing from 2 to 4 carbon atoms, per

mol. of nitrohydrocarbon, the initial concentration of said acid preferably being at least 80% by weight, and providing either initially or at a later stage of the reaction at least 1 mol. of water per mol. of nitrohydrocarbon to complete the conversion to the carboxylic acid stage. According to this reaction 1 mol. of hydroxylamine is formed 'for each mol. of carboxylic acid produced, but in the presence of the halogenated fatty acid the hydroxylamine tends to decompose to ammonia and other products. The hydroxylamine remaining in the final reaction mixture is, of course, in the form of a salt, which may be separated from the carboxylic acid and unreacted The car boxylic acid may be recovered from the reaction mixture according to known methods such as distillation or extraction.

The nitrohydrocarbons which are suitable for my process constitute the primary nitrohydrocarbons as, for example, the primary nitroparaffins, and the arylor cycloalkyl substituted primary nitroparafilns such as phenyl-nitromethane or 1-nitro-2 cyclohexyl=ethane. The primary nitroparamns containing two or more carbon atoms are particularly suited tor use in my process. Among the nitroparamns, nitroethane, l-nitropropane, i-nitrobutane, and 1-=nitro-2-methyl propane are particularly advantageous in that their boiling points constitute suitable reaction temperatures, and the reaction mixture may thus be simply refluxed to effect the conversion. lit should be distinctly understood, however, that my invention is not to be limited to any particular nitrohydrocarbons of this series, but is generally applicable to all nitrohydrocarbons containing the group -CH'z.NOz.

The acids which may be used to effect the com version of the nitrohydrocarbons in my process may be any alpha-halogenated fatty acid containing from 2 to 4 carbon atoms. Among such acids may be mentioned monochloracetic, dichloracetic, dibromacetic, trichloracetic, alphachlorpropionic, alpha-beta-dichlorpropionic, ah

pha-alphadibrompropionic, and alpha-alphadichlorbutyric. H It will be evident, oi course, that although any of these alpha-halogenated fatty acids will serve to efiect the conversion of the nitrohydrocarbon into the corresponding car--- boxylic acid, some of these acids will be less advantageous than others. Thus, I have found that some of these acids are less active than others, and must be employed in greater amounts, relative to the nitrohydrocarbon, to secure the desired degree of conversion. It will also be evident that operating conditions will govern the choice of the acid to be used as the converting agent. For example, if a relatively high reaction temperature is to be employed, acids such as trichloracetic, which have some tendency to be decomposed under the conditions of this reaction, should preferably not be employed. In view. of these considerations, i prefer to utilize dichloracetic acid, but it should be distinctly understood that my invention is not to be liraited to the use of this or any of the other acids mentioned above. Any alpha-halogenated fatty acid containing from 2 to 4 carbon atoms may be employed, and one skilled in the art can readily iii choose a suitable acid for the particular reaction conditions to be employed.

I have found that the reaction of the present invention proceeds most rapidly with very, concentrated acid solutions, but that the reaction will not proceed to completion unless 1 mol. of water per mol. of nitrohydrocarbor is provided in the reaction mixture. For example, when employing anhydrous acids, a final-conversion. of nitrohydrocarbon to carboxylic acids of the order of 50% is obtained; but optimum conversion may then be secured by introducing 1 mol. of water per mol. of nitrohydrocarbon, and continuing the reaction until the intermediate products are completely transformed to the oarbonylic acid stage. This finaiconversion usually requires only from 5 to 15 minutes at the reaction temperature. Alternatively, the additional Water may be secured by the use of very concentrated acids may cause dimculty unless adequate cooling means are provided. For this reason it may be desirable to utilize an acid solution containing a substantial amount of water, even though a lower rate of conversion is thus obtained. In general, it may be said that the preferred acid concentration is that which will give rise to a rapid conversion rate without unduly rapid evolution of heat, and which will be sufficiently miscible with the nitrohydro'carbon to insure ease of reaction. An acid of 80% to 100% concentration will usually be found to be satisfactory, and preliminary experiments will readily determine the optimum concentration for any particular acid under the reaction conditions to be employed.

The reaction temperature is preferably maintained between 100 C. and 160 C. At temperatures lower than 100 C. the reaction velocity tends to become unsatisfactorily low, and at temperatures above 160 C. there is an increased tendency for decomposition reactions to take place; It will be evident, however; that higher temperatures may be suitably employed if the s time of reaction is reduced sufllciently t6 avoid undue decomposition of the products. In a continuous process, for example, higher temperatures may be used in certain cases by increasing the space velocity in the reaction zone to a point at which the decomposition reactions proceed only to a very slight extent.

My invention may be illustrated by the following specific examples in which various nitrohydrocarbons are converted to the corresponding carboxylic acids by the use of a number of difierent types of acids as converting agents.

Example I A reaction mixture comprising 89parts by weight of l-nitropropane and 129 parts'of dichloracetic acid was refluxed with stirring for approximately '7 hours. At the end of this period, 18 parts of water was introduced, and the mix- A reaction mixture comprising 89 parts by weight of l-nitropropane. and 163 parts of trichloraceticacid was refluxed with stirring for 7 hours. water was added, and the mixture was further refluxed for 10- minutes. The following results were secured:

Yield based Conversion based Product x on nitropro ue =on nitro ropano. resc int uced Proplonicacid 43% Example 11! A reaction mixturelcomprising 89 parts by weight of i-nitropropane and '94 parts of modechloracetic acid. was refluxed for '7- hours. At the end of this period, 18 parts of water was added,

At the'end of this period, 18 partsof and the mixture was further refluxed for 10 min utes. The following results were secured:

Yield based on Conversion based Product nitropropane on nitropropane reacted introduced Propionic acid 74% 70% be carried out under super-atmospheric pressure, and by increasing the pressure a higher reaction temperature may be secured in the case of the lower boiling nitrohydrocarbons, such as nitroethane. In general, it maybe said that a pres sure should be employed which will insure liquid phase conditions at the reaction temperature utilized. Likewise, it will be evident that my invention can be carried out in a continuous manner by employing a reaction tube or vessel maintained at the desired reaction temperature, and passing the reaction mixtures through the heated zone at a space velocity suflicient to effect the desired reaction and minimize decomposition reactions. It will also be apparent that my process is applicable to the treatment of mixtures of nitrohydrocarbo'ns as well as single compounds,

and to the use of mixed acids as the converting agents, as well as the single acids employed in the above examples. All such modifications which are not excluded by the scope of the appended claims are to be considered as included in my invention.

My invention now having been described, what I claim is: a

l. A process for the production of carboxylic acids from primary nitrohydrocarbons, which comprises subjecting the hydrocarbon to the action of at least'an equimolecular amount of an alpha-halogenated fatty acid containing from 2 to 4 carbonatoms, and providing at least 1 mol. of water per mol. of nitrohydrocarbon to complete the conversion to the carboxylic acid stage.

.2.'A process for the production of fatty acids from primary nitroparafllns, which comprises subjecting the nitroparafiln at a temperature in excess of 100 C. to the action of at least an equimolecular amount of an alpha-halogenated fatty acid containing from 2 to 4 carbon atoms, the initial concentration of said acid being at least 80% by weight, and providing at least 1 mol. of

- the, concentration of said acid being such that there is present in the reaction mixture approximately 1 mol. of water per mol. of nitroparamn. A 4. A process for the production of fatty acids from primary nitroparaflins, which comprises subjecting the nitropara flin at a temperature of I 100 C. to' 160 C. to the action of at least an equimolecular amount of monochloracetic acid,

least 80% by weight, and providing at least 1 moi.

. of water per moi. of nitroparaffln to complete the subjecting the nitroparaflin at a conversion to the carboxylic acid stage.

5. A process for the production of fatty acids from primary nitroparafllns, which comprises 100 C. to 160", C; to the action of at least an ,equimoiecuiar amount of dichlor'acetic acid, the initial concentration of said acid being at least 80% byweight, and providing at least 1 mol. of water permol. of nitroparaflln to complete the conversion to the carboxylic acid stage.

g 6. A process for the production of fatty acids from primary nitroparafiins, which comprises subiectingthe nitrop'araifin at a temperature of initial concentration 80% by weight, and providing at least i moi. of

temperature of carboxylic acid stage. I v

equimoiecular amount of trichioracetic acid; the of said acid being at least water per mol. of .nitroparaflin' to complete the conversion to the carboxylic" acid stage; 'i. A process for the production of fatty acids from primary nitropans, which comprises reacting the nitroparaflln at a temperature of 100 C. to' I60 C. with at least an equimolecular amount of substantially anhydrous dichloracetic acid, and subsequently introducing at least 1 mol.

to 1 C. to the action of at least an of water per mol. of nitroparafiln and continuing the reaction to complete the conversion to the B. LIPPrNco'rT. 

